I played Kim in our AW game. Kim was an Angel by training but made her living mostly as a prostitute. She could channel the dead while having sex, though it generally wasn't something she did on purpose.
Kim had been raised by the local Cult, whose influence over the area -- founded in their access to and knowledge of advanced medical training and supplies -- was considerable, and the initial focus of our game. Kim left the cult a year or so before play began, for unspecified reasons that probably involved them trying to run her life and marry her off to a cult 'father.' The Cult's ideology consisted primarily of an interpretation of the Psychic Maelstrom -- they believed that the maelstrom was the aggregate of the spiritual and emotional state of everyone who had ever died. The cult believed that the apocalypse was the result of human suffering -- too many unhappy people died, and the maelstrom became contaminated and eventually lashed out. They wanted to reduce suffering and therefore restore the maelstrom to a preapocalyptic state. The Cult's methods were the usual cult methods: hierarchy, control, and sex.
Anyways, my guiding principle for playing Kim was that when people asked her for something, she would give it to them. She was smart enough most of the time to make sure that they paid, or to negotiate sensible terms, but if push came to shove in the end she would always say 'yes.' This really solidified for me in the third or fourth session, when the group's Brainer managed to Deep Brain Scan Kim and asked me 'In what way are your mind and soul vulnerable?' The answer was a paraphrase of the above: if someone asks for something, sincerely and with genuine emotional need, Kim will always say yes.
Interestingly enough, this did not turn out to be a major handicap in Apocalypse World. Kim's overall trajectory was from a sensible, pleading, frustrated/disappointed Angel to an angry, demanding, ass-kicking Battlebabe -- but I never really felt like she ever compromised the core of her personality. It seemed inevitable, really, but over our fourteen+ sessions I just kept helping people and giving them what they wanted as best I could -- and then pursuing what I felt to be everyone's best interests as aggressively as possible, in the meanwhile. The fiction constantly revealed that Kim felt guilty about almost everything, and took on more and more of other people's sufferings and responsibility -- but at the same time I found myself confronted with the surprising fact that she could take it. It was fun to play someone with all the characteristics of a martyr, but who ultimately had no interest in martyrdom.